Coyotes in Yellowstone National Park: the Influence

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln USDA National Wildlife Research Center - Staff U.S. Department of Agriculture: Animal and Publications Plant Health Inspection Service January 2003 Coyotes; Coyotes in Yellowstone National Park: the influence Eric M. Gese USDA/APHIS/WS National Wildlife Research Center, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/icwdm_usdanwrc Part of the Environmental Sciences Commons Gese, Eric M., "Coyotes; Coyotes in Yellowstone National Park: the influence" (2003). USDA National Wildlife Research Center - Staff Publications. 116. https://digitalcommons.unl.edu/icwdm_usdanwrc/116 This Article is brought to you for free and open access by the U.S. Department of Agriculture: Animal and Plant Health Inspection Service at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USDA National Wildlife Research Center - Staff Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. / Coyotes Coyotes in Yellowstone National Park: the influence of dominance on foraging, territoriality, and fitness I Eric M. Gese A coyote Canis latrans pauses during its travels in Yellowstone National Park O E. M. Gese. Studies on the behavioural ecology of coyotes (Canis behaviour, interactions among pack me~nbers,and latrans) areinherently difficult due to their nocturnal how they deal with changes in their environment. and secretive habits. In Yellowstone National Park From January 1991 to June 1993, over 2500 h of (YNP), Wyoming, the coyote population has not direct observatiorl were collected on members of been subject to hunian persecution for several five resident packs, five transient individuals, and decades, allowing for direct observation of the~r eight dispersing animals, in the Lamar River Valley 272 Biology and conservation of wild canids of :-.'<F. The pit>t~~ct.ol d dolninance hierarchy .Yel!ows!sne National Park within the resident packs greatly influenced access to food resources, individual fitness (i.e. mating opportunities, survival, and dispersal), and regula- Liuri of pdik size. .Alpha animals had the greatest access to ungulate carcasses in winter, diligently defended their territory against intruders, and conse- quently achieved a high degree of fitness in terms of acquiring all mating opportunities and reproductive success. Subordinate individuals (betas and pups) in the pack had less access to resources (mates and food), lower survival, higher dispersal rates, and thus reduced fitness as compared to alpha animals. Figure 17.1 Yellowstone National Park, Wyoming where the Non-territorial coyotes (transients and dispersers) study was conducted. had even lower survival (mainly dispersing animals), no mating opportunities, and little access to ungulate carcasses during winter when rcsourccs were 44"'"'JL, N, llOOlllE), about 2000 111 dtruve sed level. scarce. Being dominant and territorial was advanta- Long, cold winters and short, cool summers charac- geous in coyote society by insuring access to mates, terize the climate in the valley (Dirks and Martner food, and space. 1982; Houston 1982). Mean annual temperature and precipitation is 1.PC and 3 1.7 cm, respectively, with most of the annual precipitation falling Introduction as snow (Dirks and Martner 1982; Houston 1982). Habitats included forest, mesic meadow, mrtir shrub- The coyote, is an opportunistic, generalist predator meadow, riparian, grassland, sage-grassland, and road that has expanded its distribution to most of North (see Gese et al. 1996a for habitat descriptions). America and is probably one of the most widely Predominant ungulate species included elk (Cervu5 researclled canids. Yet, its typically nocturnal, secre- elaphw), mule deer (Odocoileus Ilemion~rs),bison, tive behaviour mean there have been only two (Bison bison), and bighorn sheep (Ovis canader7sis) studies-both in Grand Teton National Park, A few moose (Alces alces) and white-ta~leddeer Wyoming-based on direct observation of wild coy- (Oilocoileus virgi~iarzus) inhabilrcl Ll~e vdlley, and otes (Camenzind 1978b; Bekoff and Wells 1986). pronghorn antelope (Antilocaprn arner icalza) were The coyote population in YNP has not been perse- present during summer. A major food source for cuted for several decades, and thus is tolerant of coyotes during winter was elk carrion (Murie 1940, humans to an extent that has facilitated our studies Houston 1978; Gese et al. 1996a). Small mammal of how coyotes deal with fluctuatioris in tempera- species included microtines (1Microtus spp.), mice ture, snow depth, snow-pack hardness, and food (Peromyscus spp.), pocket gophers (Tlzonzonlys availability (e.g. Gese et a1. 1996a-c). This chapter tlz@oi&s), and Uinta ground squirrels (Syennoplzilr~s synthesizes the findings of over 2500 h of observa- arrnatrls). tion on coyotes in the Lamar Kiver Valley, YNP, Wyoming (Gese et al. 1996a-c; Gese and Ruff 1997, 1998; Gese 2001b). General methodology Study area The sampling design and methodologies for recording behavioural observations of coyotes were The study u.as conducted in a 70-km%rea in the described in Gese rtal. (1996a-c), Gese and Ruff (1997, Larrlar River Valley, YNP, l,\;yo~ning (Fig. 17.1; 1998), and Gese (2001). In general, coyotes >5 months Coyotes 273 of age tvere captured with padded leg-hold traps icith and used the softuvare program SYS'TAT (Wilkinson attached tranquilizer tabs, weighed, sexed, ear-tagged et al. 1992) follo~vingthe recommendations in Steel and radio-collared, and the vestigial first premolar of and Torrie (1980), Sokal and Rohlf (1981), and the lower jaw was extracted for ageing (Linhart and Zar (1996). gnowlton 1967). Pups (8-12 weeks old) were captured at the den, ear-tagged, and surgically implanted with an irltraperitoneal transmitter. We classified coyotes by Environmental conditions age as pups ((12 months old), yearlings (12-24 months old), or adults (>24 months of age). Coyotes The first winter (1990-91) of behavioural observa- were also classified as' residents or transients based tions in YNP was mild, with little carcass biomass upon their social interactions and affinity for one area available to the coyotes in the valley (Fig. 17.2(a)). (Bowen 1981; Gese et al. 1988). Members of a resident Maximum snow depth was 30 cm and the amount of pack were further classified into different social classes, known carcass biomass was <I70 kglwk. Coyotes including alphas (dominant breeding adults), betas were dependent upon small mammals, mostly voles, (adults and yearlings subordinate to the alphas but as their major food item during that winter. The sec- dominant over pups), or pups (young of the year ond winter (1991-92) was characterized by deeper subordinate to both alphas and betas), based upon the snow cover and higher carcass biomass (Fig. 17.2(b)). separate male and female dominance hierarchies That winter had an early snowfall followed by a thaw, observed in the pack (see Gese et al. 1996a-c for details which re-froze into an ice layer on the ground and on methodology). subbequently led to an early initiation of winter die- Coyotes were observed with a 10-45x spotting off of ungulates. Maximum snow depth was 46 cm, scope from vantage points located throughout the and known carcass biomass exceeded 200 kglwk for valley during October-July; high grass (>1 m) pre- 10 weeks. The third winter (1992-93) was similar . cluded observation in August and September. We to the second winter, with deep snow cover and collected nocturnal observations using an 11 x high carcass biomass (Fig. 17.2(C)).Maximum snow night-vision scope. Behavioural observations fol- depth was 63 cm, and for 6 weeks known carcass lowed Gese et d. (1996a,b) in which we randomly biomass was >200 kglwk. sampled packs, and stratified individuals within each pack to allow for similar sampling of each sex and social class. We used focal-animal sampling Social organization and dominance (Lehner 1979; Martin and Bateson 1993), recording all behaviours for a single individual using a program . From January 1991 to June 1993, we observed 49 on a notebook computer, or on a tape recorder and resident coyotes from 5 packs for 2456 h and 5 tran- transcribed later. Whenever possible, we recorded sients for 51 h; 8 animals identified as dispersers were the location at which behaviours (e.g. bed sites, observed for 53 h. Of the 54 coyotes observed, 29 dens, howling, scent-marking, predation, carcasses) were males, 23 were females, and 2 unmarked coyotes occurred to the nearest 10-m grid intersection using were of unknown sex. We collared or implanted 31 the Universal Transverse Mercator (UTM) grid system coyotes with radio-transmitters, and 23 were on a 1 : 24,000 US Geological' Survey topographic unmarked but recognizable from physical characteris- map. Snow depth, hardness, and layering were tics. The coyotes in the Lamar River Valley were orga- recorded every 1-2 days by excavation of a snow pit. nized into relatively large packs (up to 10 individuals) Additional climate information was recorded at a with distinct territories (Fig. 17.3). These resident permanent weather station within the study area. packs remained spatially stable, except in the last win- Available ungulate carcass biomass in the valley was ter (1992-93) when the Soda Butte pack usurped a part estimated weekly (see Gese et al. 1996a). The sam- of the Norris pack territory (Fig. 17.3(c); see Gese 1998 pling unit for all statistical tests was the individual for details). Transient home ranges overlapped the coyote (Machlis et al. 1985). Statistical analyses of resident territories. Territorial boundaries of resident behavimlr5 are described in Gese et al. (1996a-c) packs were scent-marked and actively defended; 274 Biology and conservation of wild canids 60 Ei Carcass biomass 500 5. - 50 cn -s 400 % 5 40 .-5 Q w 300 3 30 m0 0 200 5 s 20 10 100 0 0 J FMAM Month Figure 17.2 Mean snow depth and carcass biomass for each week during the winters of (a) 1990-91, (b) 1991-92, and (c) 1992-93 in the LamarValley,YNF: Wyoming.

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